This invention relates to aligning a fiber to an optical device.
Fiber optic systems often require aligning an optical fiber (xe2x80x9ca fiberxe2x80x9d) to couple light to an optical device, such as a laser diode or an electro-optical detector. Fibers and optical devices have very small emitting and receiving areas, sometimes as small as a few microns in diameter. Therefore, achieving an efficient coupling between a fiber and an optical device requires an alignment with sub-micron accuracy. Typically, the alignment is performed manually, by an operator, who adjusts the position of the fiber while observing the fiber with an observation station (i.e., a high-resolution camera or microscope) or while monitoring a measured output signal from the optical device. Manual alignment is very time consuming and the resulting alignment is dependent on the accuracy and skill of the individual operator.
According to an aspect of this invention, an apparatus for aligning a fiber to an optical device includes a base, a fiber holder mounted on the base, the fiber holder holding the fiber during operation of the apparatus, a first movable stage mounted on the base, the first movable stage holding the optical device during operation of the apparatus, a second movable stage mounted on the base, wherein the second movable stage is configured to move parallel to the first movable stage, a fiber positioner attached to the second movable stage, and a processor programmed to control the movement of the first movable stage and the second movable stage, wherein, during operation of the apparatus, the processor moves the first movable stage and the second movable stage towards the fiber.
One or more of the following features may also be included: during operation of the apparatus, the processor moves the first movable stage and the second movable stage towards the fiber until the end of the fiber is proximate to the optical device, the fiber positioner may include a movable arm having a range of motion orthogonal to the longitudinal axis of the fiber held in the fiber holder, wherein the processor is programmed to control the movement of the movable arm, and wherein, during operation of the apparatus, the processor moves the movable arm and positions an end of the fiber proximate to the optical device, the apparatus may include a signal generation circuit transmitting a test signal to one of the optical device and the fiber, and a signal detection circuit receiving a detected test signal from one of the optical device and the fiber, wherein the processor is programmed to determine the optimum position of the fiber to maximize a strength of the detected signal, the apparatus may include a support member attached to the base, and a camera mounted to the support member, the camera having a focal plane proximate to the end of the fiber, and, wherein the processor is programmed to determine the coordinates of the end of the fiber that is being aligned to the optical device, and, wherein the movable arm further includes a fiber-guide holding device attached to an end of the movable arm, wherein, during operation of the apparatus, the fiber-guide holding device holds the fiber-guide using forces associated with a flow of air, and, wherein the movable arm further includes a fiber-guide holding device attached to an end of the movable arm, wherein the fiber-guide holding device is a clamping device, and, wherein the optical device is mounted within a device box, and wherein the device box has an opening in a side of the device box that is in substantial alignment with the optical device, and apparatus may further include a third movable stage mounted to the support member and holding an adhesive applicator, wherein, during operation of the apparatus, the adhesive applicator holds an adhesive, and wherein the processor is programmed to control the movement of the third movable stage and programmed to control the dispensing of the adhesive proximate to at least one of the fiber, the fiber-guide and the device box, and apparatus may further include an adhesive applicator attached to the second movable stage, wherein, during operation of the apparatus, the adhesive applicator holds an adhesive, and, wherein the processor is programmed to control the dispensing of the adhesive proximate to at least one of the fiber, the fiber-guide and the opening in the side of the device box, and the apparatus may further include a third movable stage mounted to the support member and holding an adhesive applicator, wherein, during operation of the apparatus, the adhesive applicator holds an adhesive, and wherein the processor is programmed to control the movement of the third movable stage and programmed to control the dispensing of the adhesive proximate to at least one of the fiber and the fiber-guide, and, wherein the fiber holder includes a fiber rotator for rotating the fiber about its longitudinal axis, and wherein the processor is programmed to rotate the fiber until the detected test signal is maximized.
According to a further aspect of this invention, an apparatus for aligning a fiber to an optical device includes a base, a fiber holder mounted on the base, the fiber holder holding the fiber during operation of the apparatus, a first movable stage mounted on the base, the first movable stage holding the optical device during operation of the apparatus, a support member attached to the base, a camera mounted to the support member, the camera having a focal plane proximate to an end of the fiber that is being aligned to the optical device, and a processor programmed to control the movement of the first movable stage, wherein, during operation of the apparatus, the first movable stage is moved towards the fiber.
One or more of the following features may also be included: wherein the processor is programmed to determine the coordinates of the end of the fiber that is being aligned to the optical device, and, wherein the optical device is mounted within a device box, and wherein the device box has a feed-through opening in a side of the device box that is in substantial alignment with the optical device, and the apparatus may further include a signal generation circuit transmitting a test signal to one of the optical device and the fiber, and a signal detection circuit receiving a detected test signal from one of the optical device and the fiber, wherein the processor is programmed to determine the optimum separation distance between the fiber and the optical device to maximize a strength of the detected signal, and, wherein the fiber holder includes a fiber rotator for rotating the fiber about its longitudinal axis, and wherein the processor is programmed to rotate the fiber until the detected test signal is maximized.
According to a further aspect of this invention a method of aligning a fiber to an optical device includes holding a fiber in a fixed position, holding an optical device on a first movable stage, holding a fiber-guide on a second movable stage, and moving the optical device and the go fiber-guide towards the fiber, wherein the moving the optical device and the fiber-guide towards the fiber comprises controlling the moving with a processor.
One or more of the following features may also be included: wherein the holding a fiber-guide further includes holding the fiber-guide with a movable arm having a range of motion orthogonal to the longitudinal axis of the fiber, and moving the fiber-guide proximate to the optical device under control of the processor, the method may further include transmitting a test signal to one of the fiber and the optical device, receiving a signal from one of the fiber and the optical device, and determining the optimum position of the fiber with the processor, the determining based on a signal strength of the received signal, and, wherein holding a fiber in a fixed position further includes holding an end of the fiber in a focal plane of a camera, the method may further include determining coordinates of the end of the fiber with the processor, the determining the coordinates based on an output signal from the camera, and, wherein holding the fiber-guide further includes holding the fiber-guide with a force associated with a flow of air, and, wherein holding the fiber-guide further includes holding the fiber-guide with a clamping force, and, wherein the optical device is mounted within a device box, wherein the device box has an opening in the side of the device box, and wherein holding the device box further includes holding the device box with the opening in substantial alignment with the longitudinal axis of the fiber, the method may further include dispensing adhesive proximate to one of the fiber-guide, the fiber and the optical device, wherein the dispensing adhesive may further include moving an adhesive applicator under control of the processor, and dispensing adhesive from the applicator under control of the processor, the method may further include rotating the fiber with a fiber rotator under control of the processor, and determining, by the processor, the optimum rotational position of the fiber based on a signal strength of the received signal.
According to a further aspect of this invention a method of aligning a fiber to an optical device includes holding a fiber in a fixed position, wherein an end of the fiber is located in a focal plane of a camera, holding an optical device on a first movable stage, moving the optical device towards the fiber, the moving comprises controlling the moving with a processor.
One or more of the following features may also be included: determining coordinates of the end of the fiber with the processor, the determining based upon an output signal from the camera, and, wherein the optical device is mounted within a device box, wherein the device box has an opening in the side of the device box, and wherein holding the device box further includes holding the device box with the opening in substantial alignment with the longitudinal axis of the fiber, the method may further include transmitting a test signal to one of the fiber and the optical device, receiving a signal from one of the fiber and the optical device, and determining the optimum position of the fiber with the processor, the determining based on a signal strength of the received signal, the method may further include rotating the fiber with a fiber rotator under control of the processor, and determining, by the processor, the optimum rotational position of the fiber based on a signal strength of the received signal.
Embodiments of the invention may have one or more of the following advantages. For example, the use of automated movers reduces the manual handling of a fiber during alignment to an optical device and reduces the time required to perform an alignment. Holding the fiber stationary while moving the optical device into alignment reduces the stresses applied to the fiber, reduces the possibility of damaging the fiber and reduces possible fluctuations in a light beam emitted from the fiber (i.e. the intensity or phase of the emitted light beam). Holding the fiber stationary also reduces the complexity, and therefore the cost, of the apparatus by requiring fewer movable stages. Some of the embodiments include a camera that is held stationary and with a fixed focal plane near the end of the fiber that is being held stationary while the optical device is being aligned with it. This eliminates the need to move the camera to track the end of the fiber during the alignment. In some embodiments a fiber rotator is used to rotate a fiber along its longitudinal axis, therefore setting the polarity of the fiber end to match the polarity of the optical device. This fiber rotator may also include a clamping mechanism for holding the fiber. In some embodiments adhesive is dispensed before or after the fiber is aligned to the optical device.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
FIG. 1A shows a side view of a fiber to optical device alignment system in a start position;
FIG. 1B shows the fiber to optical device alignment systems of FIG. 1 in an intermediate position;
FIG. 1C show the fiber to optical device alignment system of FIG. 1 in a final alignment position;
FIG. 2A shows a side view of a fiber holder with rotating mechanism;
FIG. 2B shows a front view of a fiber holder with rotating mechanism;
FIG. 3A shows a front view of a fiber-guide holder holding a fiber-guide;
FIG. 3B shows a side cross-sectional view of the fiber-guide of FIG. 3A with a fiber inserted;
FIG. 3C shows a side view of a second embodiment of a fiber-guide holder clamp holding a fiber-guide;
FIG. 3D shows another view of the fiber-guide holder clamp of FIG. 3C;
FIG. 4 shows an adhesive applicator and ultra-violet curing light attached to the system of FIG. 1.
Like reference symbols in the various drawings indicate like elements.